1. Field of the Invention
The present invention relates to an apparatus for filling a vessel with high pressure gas and thereafter sealing the vessel, and more particularly, relates to an apparatus for filling an air bag canister with high pressure gas and sealing the end wall of the canister.
2. Description of the Related Art
An apparatus for supplying gas under high pressure to a weldable air bag canister and thereafter sealing the air bag canister are known in the art. Such known apparatus includes a gas fill and weld head assembly having a weld head with a primary bore therein, in which a welding electrode is disposed. A weld ball feed system includes a plurality of pistons slidably disposed in a plurality of respective passageways. By controlling the sliding movement of the pistons, individual weld balls may be supplied to the primary bore from an external feed source. A problem with such an apparatus, however, is that the weld ball feed system is exposed to the high pressure of the gas when the air bag canister is filled. Consequently, a plurality of seals must be used between the reciprocating pistons and the passageways to prevent gas leakage to the outside ambient environment. Such seals may fail over a period of time and thereby allow escape of the gas to the outside ambient environment, which is not desirable.
Another problem with such conventional designs is that each separate piston requires a separate drive mechanism for reciprocating the piston within the respective passageway. The multiplicity of such required drives increases the complexity and cost of the system, as well as adding another possible source of failure.
What is needed in the art is an apparatus for filling and sealing a weldable vessel which can supply weld balls to a weld head assembly while being fluidly disassociated from the weld head assembly. Such an apparatus would accordingly not require the plurality of seals used in known apparatus, and thereby avoid disadvantages associated therewith.